CORVALLIS -- Thousands of college students regularly hit the cardio exercise machines to work off stress after an exam or stay in shape. Oregon State University is harnessing the energy the machines can generate and converting it to electricity to feed back into the power grid.

It is among the first universities in the United States to do so.

With new technology developed by a Florida firm, OSU has retrofitted 22 elliptical exercise machines in its student-fee-funded Dixon Recreation Center and already is collecting the power produced by students.

The effort will produce an estimated 3,500 kilowatt hours of electricity in a year, according to Brandon Trelstad, the university's sustainability coordinator.

Its output could be equivalent to what is needed to power a small, efficient house, Trelstad said. "Our ultimate goal is to maximize both the real power output of the system and the learning opportunities gained by having it at OSU."

In 2007, OSU students voted to tax themselves $8.50 per student per term to purchase renewable energy for the campus. Since then, about three-quarters of the university's electricity has come from renewable production.

"OSU students have demonstrated how big student power can be on campus," said Matthew Pennington, chief of staff for the Associated Students of Oregon State University. "It was a grass roots movement that helped OSU turn green, and this project moves it forward even farther."

The ReRev technology features a system with a pending patent called ReCardio that captures and converts the otherwise-counterproductive heat energy from exercise machines.

Though some businesses or individuals have dabbled with this type of energy conversion, a program on this scale is unusual, Trelstad said.

"A battery-free system like this, tied to the grid, is quite rare," Trelstad said. "In fact, we're informed by ReRev, which has done extensive market research, that this is the largest installation of its kind in the world."